Remodeling the Wastewater Stream for Energy Recovery
"Recycled water is a new
energy source," said Grant Davis, assistant general manager of the
Sonoma County Water Agency. "Water and wastewater that you'd normally
have to treat and dispose of will become the source for heating and
cooling."
They estimate savings of 90 percent on natural gas and about 50 percent on electricity for heating and cooling. The environmental benefits are hard to quantify - but the county is working on it. Under the wastewater recycling plan, 55- to 60-degree water would be pumped from the treatment plant to the business park through underground pipes into a pump inside each building. Once in the pump, a refrigeration device transfers heat to or from the wastewater. A compressor converts that heat energy into warm or cold air that can be pushed through about 3 million square feet of office space at the business park, replacing the traditional heating and air conditioning systems.
In this "open" system, the water could also be used to irrigate landscaping, or, with a secondary set of pipes, flush toilets. Otherwise, the chilly or hot water - between about 40 degrees and 150 degrees - would pass through underground pipes to two adjacent reservoirs.
The wastewater recovery system could work particularly well for small or midsize cities or suburbs where the energy needed to pump water to low-slung buildings is much less than for skyscrapers.
Why?
"We all know California will have severe droughts in the next 20 to 40 years and that will affect water supply," said Gary Geernaert, director of the Institute of Geophysics and Planetary Physics at Los Alamos National Lab. "This will help us make educated guesses about what the pressures will be on the public and private infrastructure and help build that into the design."
The project has gained steam in the past few months as Pacific Gas and Electric Co. and some of the biggest names in the wine business have signed on; in March, county supervisors approved $1 million for a feasibility study. The flurry of interest comes as more cities and businesses take a hard look at their contributions to greenhouse gas emissions and climate change, and national labs expand their research to include not just military security, but water, energy and economic security.
Sonoma officials will meet with lawmakers in Washington about allocating money for this project and establishing a fund, similar to the Community Development Block Grant Program, to pay for similar projects all over the United States. In addition to federal money, Sonoma is considering revenue bonds and creating a special assessment district.They estimate savings of 90 percent on natural gas and about 50 percent on electricity for heating and cooling. The environmental benefits are hard to quantify - but the county is working on it. Under the wastewater recycling plan, 55- to 60-degree water would be pumped from the treatment plant to the business park through underground pipes into a pump inside each building. Once in the pump, a refrigeration device transfers heat to or from the wastewater. A compressor converts that heat energy into warm or cold air that can be pushed through about 3 million square feet of office space at the business park, replacing the traditional heating and air conditioning systems.
In this "open" system, the water could also be used to irrigate landscaping, or, with a secondary set of pipes, flush toilets. Otherwise, the chilly or hot water - between about 40 degrees and 150 degrees - would pass through underground pipes to two adjacent reservoirs.
The wastewater recovery system could work particularly well for small or midsize cities or suburbs where the energy needed to pump water to low-slung buildings is much less than for skyscrapers.
Why?
"We all know California will have severe droughts in the next 20 to 40 years and that will affect water supply," said Gary Geernaert, director of the Institute of Geophysics and Planetary Physics at Los Alamos National Lab. "This will help us make educated guesses about what the pressures will be on the public and private infrastructure and help build that into the design."
SOURCE: April 2008 SFGATE.com
